It exports the following functions to the caller's scope, to be used by Perl's Unicode matching system: InEastAsianFullwidth, InEastAsianHalfwidth, InEastAsianAmbiguous, InEastAsianNarrowInEastAsianWide, InEastAsianNeutral.

In accord to TR11 cited above, two additional context-sensitive properties are exported: InFullwidth (union of Fullwidth and Wide) and InHalfwidth (union of Halfwidth, Narrow and Neutral).

Ambiguous characters are treated by default as part of InHalfwidth, but you can modify this behaviour by assigning a true value to $Unicode::EastAsianWidth::EastAsian at compile time within a BEGIN block before loading this module:

Setting $Unicode::EastAsianWidth::EastAsian at run-time used to work on Perl versions between 5.8 and 5.14 due to an implementation detail, but it will no longer work on Perl 5.16 and later versions, and hence is not recommended.